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Full Version: hp49g+ bug? Combinations, sums, and equivalence
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The following is true:
COMB(n, 2) + n = Sum of all integers from 1 to n

i.e. if n = 5

COMB(5, 2) + 5 = 5! รท (3!*2!) + 5 = 10 + 5 = 15
1 + 2 + 3 + 4 + 5 = 15

However, when I input
'COMB(5,2) + 5' on one level,
and '[Capital Sigma symbol](X=1,5,X)' on the other,
and I execute the == command on the Program-Test Menu, I get a 0 as a result (incorrect result)

Both objects inputed are same type (9 - algebriac expressions?).

A bug in the 49g+ CAS perhaps.

In the stack I can't recreate your bug: I do:
Experssion 1 [ENTER]
Expression 2 [ENTER]
== [EVAL] I get 1.

If I put the same in a program, I get 0.



the 0 doesn't mean 'incorrect result'.

The result is correct, the expressions are simply not the same,

as you can easily see on the stack.

Maybe it also depends on the status of the evaluation flags,

this may be a case for RTFM;-)


Seems to be one of the "features of the calc

Using Approx ~ mode or reals (5.) will give the correct answer.



RTFM ~ Read The 'Fascinating' Manual...;-)

As VPN pointed out, the result seems to depend on either the mode,

and/or the type of arguments.


Which is actually taken as a friendly reminder or suggesttion among friends. It only shows irritation when you get to, "RTFM-41" which means, "read the "funny" manual for once!"

Another version is RTFD41 for which "D" stands for "drawing" as in mechanical drawing.